A plug-in connector generally of the kind to which the present invention relates is known from German patent DE 10 2008 013 565 A1.
The locking arms reach therein with their locking cams behind the annular collar of an inserted mating plug-in connector. The locking arms each have therefor a radially outwardly directed graded section, at whose free end is located the respective locking cam. In this way is obtained an enlarged diameter of the plug-in connector, so that the required installation space must be accordingly enlarged. In order to keep the length of the plug-in connector as small as possible, it is also necessary to provide axially running opening areas for accommodating the graded section with enlarged diameter, whereby the penetration of dirt particles is facilitated when the adapter sleeve is not plugged in. There is, moreover, a risk that an undesirable release can occur when the mating plug-in connector is plugged together, since the operating sections that project over the periphery of the sleeve section are easy to access.
From patent DE 10 2011 084 988 is known a plug-in connector, in which the positive locking means located at the free end of the locking arms are formed on the outside thereof. The locking cams are likewise located on the lower side of these locking arms, so that the locking cams are located within the sleeve section. This arrangement and configuration of the positive elements and the locking cams require, on the one hand, a relatively elongated design of the sleeve section, and furthermore a relatively large section is located within the wall of the sleeve section, so that the locking arms are unprotected, and dirt can furthermore easily penetrate into the sleeve section.